Al 43415, the 'Waterborne Emerging Diarrheal Diseases Study' or WEDDS study, is designed to link environmental emerging waterborne disease pathogens, especially Cryptosporidium parvum, with disease in human hosts. The central hypothesis of this study is that drinking water that meets current public health standards is nonetheless a source of exposure to this class of emerging pathogens. The WEDDS specific aims remain:I. Construct, and clinically follow over time, a cohort of mfants and children and their families, closely monitoring their clinical and immunological status concerning Cryptosporidium via fecal sampling, serological testing, and assays of ceilular immunity.2. Quantify childhood population-wide infection rates with Cryptosporidium via repeated large, prospective, anonymous pediatric point-prevalence serological surveys.3. Evaluate the temporal and seasonal associations between indicators of Cryptosporidium contamination in three major drinking water supplies, and the various measures of human exposure, infection, and disease described in Specific Aims 1 and 2, and in HMO gastroenteritis datasets.4. Validate this approach by (4a) linking patient and environmental oocysts using molecular methods, and (4b) monitoring the presence of Giardia and microsporidia in water supplies.The specific aim of this supplemental proposal is to quantify the patterns and extent of gastroenteritis and cryptosporidiosis in Massachusetts elderly, using sophisticated mathematical tools, standardized serological testing, and geographical information systems mapping, and compare this information with that obtained from our other sentinel population, children, which are being studied in the parent WEDDS grant. In this study we will:1. Quantify the incidence of GI infectious a) among elderly in Massachusetts in 1990-2000 using HCFA records, and records of laboratory-confirmed cases of cryptosporidiosis via the Massachusetts passive surveillance system; and b) among elderly in the Boston metropolitan area in 1998-2001 using records of gastrointestinal infections and seroprevalence of antibodies in samples obtained via an intervention trial based in Massachusetts nursing homes;2. Examine the link between the gastrointestinal illness and drinking water supply using Geographical Information Systems and spatial statistical analysis.